bird's nest vs roost

bird's nest

noun
  • A structure built by a bird as a place to incubate eggs and rear young. 

  • Any of several plants having some resemblance to the typical nest of a bird, eg, wild carrot (Dauca carota) 

  • Any tangle of fibers resembling a typical nest of a bird. 

roost

noun
  • The place where a bird sleeps (usually its nest or a branch). 

  • A group of birds roosting together. 

  • A tidal race. 

  • A bedroom 

  • The inner roof of a cottage. 

verb
  • to spend the night 

  • To settle on a perch in order to sleep or rest 

How often have the words bird's nest and roost occurred in a corpus of books? (source: Google Ngram Viewer )